Messages in this thread | | | Date | Sun, 21 Jul 2013 18:49:40 +0200 | Subject | Re: [PATCH 1/3] misc: Add crossbar driver | From | Linus Walleij <> |
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On Thu, Jul 18, 2013 at 8:56 PM, Nishanth Menon <nm@ti.com> wrote:
> I carry forward my TI internal objection to this approach:
It is actually a very good sign of FOSS-maturity that you as a company take unresolved architectural issues to the community. Kudos!
> Lets see what happens as a result of this: > > https://patchwork.kernel.org/patch/2825148/ (introducing DTS for DRA7) > uart1 to uart6 is defined. while in fact 10 uarts exist on IP block. > uart1: serial@4806a000 { > <snip> > + interrupts = <0 72 0x4>; > Assumes that GIC interrupt by default mapping used.
So introducing this inbetween the GIC lines and its actual device IRQ lines inevitably means that the GIC three-cell concept is completely ill-devised to handle this.
For routing IRQs, I think the proper solution would be to use a cascaded struct irqchip, which in turn contains an irqdomain translation to remux the signal onto the GIC inputs.
I.e. the interrupt-controller given to that serial would be the crossbar irqchip, and that in turn will hog and allocate apropriate lines from the gic to it would probably itself list *all* the IRQs of the GIC as "its" IRQs.
We already have plenty of cascading irqchips such as GPIO controller providing IRQs, just that they only multiplex on a single GIC line instead of the whole lot.
Mock example:
intc: interrupt-controller@0 { compatible = "arm,cortex-a9-gic"; #interrupt-cells = <3>; #address-cells = <1>; interrupt-controller; reg = ...; };
crossbar: crossbar@0 { compatible = "..."; interrupt-controller; #interrupt-cells = <1>; interrupt-parent = <&intc>; interrupts = <0 0 IRQ_TYPE_LEVEL_HIGH>, <0 1 IRQ_TYPE_LEVEL_HIGH>, <0 2 IRQ_TYPE_LEVEL_HIGH>, .... <0 n IRQ_TYPE_LEVEL_HIGH>; };
uart0: serial@0 { compatible = "..."; interrupt-parent = <&crossbar>; interrupts = <1234>; };
Maybe the interrupts provided from crossbar cannot even be specified by a number, maybe a line name need to be used or so. I don't know the particulars.
Whether this as a whole is a good idea, I don't know, but you would have to go about it something like this.
What happens if there is no line to mux in a certain IRQ?
Yours, Linus Walleij
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